I have been using bottles of fluid labled "Power Steering Fluid" which can be found at any auto parts store without any ill effects. My car is only 6 years older than yours, and specifies ATF, though new ATF has come a long way since 1982 and has caused leaks in some cars of my vintage that specify ATF. Usually when MB specifies to use their fluid only, such as SLS fluid or coolant, they've got a pretty good reason, so I'd follow their spec this time. If 25 mi is too far to drive, I'm sure Phil can take an order for you and ship it to your front door.
Order here:http://catalog.peachparts.com/
Power Steering Fluid is part number 000-989-88-33.

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'81 MB 300SD, '82 MB 300D Turbo (sold/RIP), '04 Lincoln Town Car Ultimate

Sooner or later every car falls apart, ours does it later!
-German Narrator in a MB Promotion Film about the then brand new W123.